This invention relates generally to a charging device feeding an enclosure and/or blast furnace or the like. More particularly, this invention relates to a charging device for feeding or delivering to an enclosure or blast furnace with a predetermined flow rate of a solid material.
Devices of this sort are used, for example, in blast furnaces, more specifically in blast furnaces which are equipped with a tilting and/or rotary distribution chute. The hopper then constitutes a receptacle for vertically sealing off the charging material and furthermore includes a lower sealing member which makes it possible to isolate the hopper with respect to the pressurized furnace.
Such a device, which is designed to equip a blast furnace furnished with a rotary or tilting distribution chute, is known from Patent document U.S. Pat. No. 4,514,129. There is disclosed, in this document, a combined member for retaining and for regulating the flow rate of material, which comprises two registers in the form of spherical or cylindrical caps. The relative motion of these two caps makes it possible to vary the passage section symmetrically about the central outflow axis of the material. These registers are set out in a leaktight chamber, situated directly below the hopper. This leaktight chamber is equipped at its lower end with the lower sealing member. The lower sealing chamber comprises a shutter which can be pivoted between a lateral position, in which it is sheltered from the material discharged from the hopper, and a closing off position, in which it is transverse to the outflow axis of the material. In this closing off position, the shutter can be applied, through an axial transnational motion, onto a seat. This seat peripherally surrounds the discharge opening of the hopper, and is equipped with a sealing surface pointing downwardly, that is to say in the direction of outflow of the material.
A device of the sort described in Patent document U.S. Pat. No. 4,514,129, is capable of giving complete satisfaction from the point of view of regulating the flow rate and from the point of view of settling, even for an enclosure in which high working pressures prevail. Its only drawback is its high assembly height, which results from the fact that the combined member for retaining and for regulating the flow rate of material and the sealing member are superimposed below the hopper. To overcome this drawback, if required, it would, for example, be possible to envisage replacing the member for regulating the flow rate located below the hopper by a member for regulating the flow rate incorporated directly into the hopper.
From Patent document U.S. Pat. No. 4,512,702, a device is known for charging a blast furnace, of the sort described hereinabove, which is equipped with a combined member for retaining and for regulating the flow rate Of material. This device comprises a bell which is incorporated into the materials hopper. This bell, which has the form of an axisymmetric cone flaring out in the direction of its lower edge, can be moved vertically along the axis of the hopper. In the lowered position, it interacts with a first seat set out at the level of the discharge opening of the hopper in order to close the above mentioned hopper off. In the raised position, it defines an annular outflow opening between the funnel-shaped wall of the hopper and its lower edge. The passage section of this annular opening depends on the vertical travel of the bell. Now, it is well known that with a bell of this sort, there is no guarantee of satisfactory regulation of the flow rate of material. In order to alleviate this drawback, Patent document U.S. Pat. No. 4,512,702 proposes equipping the bell, on the side of its lower edge, with an oblong and pointed body which is coaxial with the central axis of the discharge opening and which extends axially through the discharge opening in the direction of the pipe for feeding the chute. The profile of this body should then theoretically make it possible to determine the regulation characteristic, that is to say the function "flow rate of material/vertical travel of the retaining and regulating member". The result obtained is, however, rather disappointing.
Patent document EP-A-0 088 253 also proposes a lower sealing member which is incorporated into the hopper. This sealing member comprises a closing off disc, which is set out below the bell and equipped with a peripheral seal on the side of its lower face. When the bell bears on its seat, the disc may be applied axially to a second seat. The second seat, which is situated below the first seat, has a passage section which is smaller than the first seat and is equipped with a sealing surface pointing towards the inside of the hopper. This leaktight member does not, however, give satisfaction. Indeed, this second seat, which is exposed to wear by the materials flowing out through the discharge opening, is rapidly deteriorated and is therefore no longer capable of ensuring closure which is leaktight with respect to the pressurized gases.
Now, on the other hand, if it is desired, in the charging device of Patent document U.S. Pat. No. 4,512,702, to replace the lower sealing member incorporated into the hopper, by a pivotable sealing shutter, of the type which is known from Patent document U.S. Pat. No. 4,514,129, any advantage from the assembly height point of view is lost. Indeed, when the bell is bearing on its seat, the above mentioned oblong and pointed body is necessarily situated below the discharge opening of the hopper. Since the pivotable sealing shutter cannot pass through the oblong body, it is consequently necessary to provide, below the materials hopper, a leaktight chamber into which this oblong body can penetrate with its entire length. The sealing shutter will then be incorporated into the lower end of this leaktight chamber, the height of which is certainly not less than the height of the leaktight chamber enclosing the above mentioned registers in the form of spherical caps which are known from Patent document U.S. Pat. No. 4,514,129.
It is obvious that there is a need to provide a charging device in which the member for retaining and for regulating the flow rate of materials is incorporated into the hopper, but which does not have all the disadvantages mentioned hereinabove for the device of Patent document U.S. Pat. No. 4,512,702.